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DIY LM386 Guitar Amp with gain and distortion control

Over the years i made a lot of diy guitar amps but this is the first time i use the LM386. I made transistors and IC based guitar amps but never a DIY LM386 guitar amp, so i ordered some LM386 on ebay and i googled LM386 guitar amp to get some inspiration then i found this awesome website: runoffgroove, i was going to make his circuit but i didn’t have FETs at the time and i didn’t want to wait for them, so i design mine with a 2N3094 instead of a MPF102, and to make it even more cooler i added a drive potentiometer, clipping diodes and a gain booster aka 11 switch ?

Schematic & PCB:

diy homemade guitar amp lm386

Circuit description: The diy LM386 guitar amp has 2 stages the pre-amp (input stage) and the power amp (output stage) like every guitar amp, the pre-amp is just one transistor biased by R1 and R2 ( R1 is the feedback resistor ) its gain is set by the Emitter resistor R3 (the higher  R3 the lower the gain), the drive POT is the input resistor it limits the gain ans sets the impedance ( increase its value for more clean control ), C1 is the input coupling capacitor (increase its value for more bass). C3 is a bypass capacitor, the audio/AC signal sees it as low impedance thus increase the gain by using 9v instead of 4.5v, D1 and D2 are the clipping diodes, C2 is a coupling capacitor it forms a high pass filter with the Vol POT (increase C2 for more bass).

The power stage is the LM386 at it’s minimal parts configuration (see the datasheet for more), C4 is another coupling capacitor that prevents the DC voltage of the pin 3 of the LM386 to go back to the clipping diodes (it’s not necessary if there is no clipping diodes), C5 and R4 is a Zobel network, C6 is a coupling capacitor that lets only the amplified AC signal to go to the speaker. C7 is a bypass capacitor it’s not in the LM386 datasheet but i found it to be necessary to prevent the LM386 from motorboating (the closer it is to the lm386 the better).

Parts list & Tools:

[table colwidth=”50|100|50|100″ colalign=”left|left”]
C1 C4, 100nF, R4,10Ω
C2, 1uF, R5,1K
C3, 10uf,Drive Volume, 100k log
C5, 47nF,Q,2N3094
C6 C7, 100uf C6 can be 220uf,Ic,LM386
D1 D2, 1N4148,Mono jack,6.3mm
D3, Red LED,DC jack,
R1, 2.2M,SW, SPDT
R2, 4.7K,Protoboard,
R3, 470Ω,,
Also a speaker is needed (8Ω), a speaker with its case like mine would save you a ton of time.

diy homemade guitar amp lm386
If you’re going to use a plastic case you will need Aluminum tape for shielding/grounding, an alternative to the Aluminum tape is to solder a copper wire to the parts that needs grounding (Pots, switches and the input jack).

I wont put the tools list because every body has different tools, but you can see the tools i used in the picture:

diy homemade guitar amp lm386


Making the circuit:

To make the PCB faster and easier i printed the inverted copper side of the PCB and i marked the traces and the components layout on the Protoboard

Making the case:

After i opened the speaker i put some painters tape on top of it then i marked the holes location and i pre-drilled them with 4mm drill bit

Then i drilled every hole with the corresponded drill bit diameter.

The thing i did not take in concentration before drilling is the mounting holes of the speaker so i had to clear space for the pots and the switches.


This Post Has 3 Comments

  1. Alex

    This is a fantastic project. Thanks for sharing. I will do it soon, that’s for sure!

  2. Kevin

    Gonna have a go at building your amp circuit, but have a question. Pins 1 and 8 on the LM386.. It appears they don’t connect to anything, yet other designs I see sometimes have a potentiometer connected between them for gain (?) control.


    1. Doruk

      Hello Kevin. When gain pins of LM386 is not connected to anything LM386’s gain is 20. If you want higher gains you can connect a capacitance between pin 1-8 but signal can be distorted with high gain . There is a trade off I guess. About potentiometer there is a 1.35k resistance between pin 1 and 8. If you connect a resistance between pin 1 and 8 you can adjust this section’s resistance hence you change a transistor’s bias current which is inside the LM386. I guess again that potentiometer best way to adjust gain is add a capacitance and a potentiometer.

      PS: I haven’t tried these on experimental circuit. I am talking with respect to videos that I watch. You can research more about LM386.

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